Analysis of Radome Induced Cross Polarization
Abstract
Streamlined radomes will always introduce depolarization because of the fact that any material surface viewed at an oblique angle has different transmission coefficients for fields polarized parallel and perpendicular to the plane of incidence, a phenomenon known as divorce. The cross polarized fields are similar in nature to those responsible for Condon lobes of parabolic reflectors, and which are known to make those antennas susceptible to crosspolarization jamming. The relative strength of those lobes is directly related to the amount of divorce, and is quite sensitive to the phase difference of parallel and perpendicular transmission coefficients. A mere 20 deg of phase divorce has a comparable effect to 3 dB of amplitude divorce. This paper presents a detailed analysis for general radome shapes, based on geometrical optics (ray tracing). Example results are presented for conical and tangent ogive radome geometries used in conjunction with a circular-aperture antenna that is mechanically scanned. The results show that when the antenna is scanned off axis, the cross-polarized pattern changes from a Condon lobe structure to a difference pattern in the direction orthogonal to the axis of scan, e.g.: under azimuth scanning the cross-polarized sum pattern resembles an elevation difference pattern, while the cross-polarized elevation difference resembles a sum beam. Hence, interference in the cross polarization will introduce a tracking error in the direction orthogonal to the scan plane.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1992
- Accession Number
- ADA249773
Entities
People
- Daniel T. Mcgrath
Organizations
- Wright Laboratory